BACKGROUND: HIV-1 incidence estimates and correlates of HIV-1 acquisition in African MSM are largely unknown. METHODS: Since 2005, HIV-1-uninfected men who reported sex with men and women (MSMW) or sex with men exclusively (MSME) were followed at scheduled visits for collection of behavioural and clinical examination data and plasma for HIV-1 testing. Urethral or rectal secretions were collected from symptomatic men to screen for gonorrhoea. Poisson regression methods were used to estimate adjusted incidence rate ratios to explore associations between risk factors and incident HIV-1 infection. Plasma viral loads (PVLs) were assessed over 2 years following seroconversion. RESULTS: Overall HIV-1 incidence in 449 men was 8.6 [95% confidence interval (CI) 6.7-11.0] per 100 person-years. Incidence was 5.8 (95% CI 4.2-7.9) per 100 person-years among MSMW, and 35.2 (95% CI 23.8-52.1) per 100 person-years among MSME. Unprotected sex, receptive anal intercourse, exclusive sex with men, group sex, and gonorrhoea in the past 6 months were strongly associated with HIV-1 acquisition, adjusted for confounders. PVL in seroconverters was more than 4 log10 copies/ml at 230 (73.4%) of 313 visits in MSMW and 153 (75.0%) of 204 visits in MSME. CONCLUSION: HIV-1 incidence is very high among MSM in coastal Kenya, and many seroconverters maintain high PVL for up to 2 years after infection. Effective HIV-1 prevention interventions, including treatment as prevention, are urgently needed in this population.